Johannes Kepler: Force

“Indeed I reply in a single word to the sentiments of the saints on these questions about nature; in theology, to be sure, the force of authorities is to be weighed, in philosophy, however, that of causes.”

Johannes Kepler

Therefore, a saint is Lactantius, who denied the rotundity of the earth; a saint is Augustine, who, admitting the rotundity, yet denied the antipodes; worthy of sainthood is the dutiful performance of moderns who, admitting the meagreness of the earth, yet deny its motion. But truth is more saintly for me, who demonstrate by philosophy, without violating my due respect for the doctors of the church, that the earth is both round and inhabited at the antipodes, and of the most despicable size, and finally is moved among the stars.
Vol. III, p. 156
Joannis Kepleri Astronomi Opera Omnia, ed. Christian Frisch (1858)

Question , Nature

“Discover the force of the heavens O Men:
Once recognised it can be put to use:
No use could be seen in unknown things.”
Vim coeli reserate viri: venit agnita ad usus: Ignotae videas commoda nulla rei.

Johannes Kepler

De fundamentis astrologiae certioribus [On the more Certain Fundamentals of Astrology or On Giving Astrology Sounder Foundations] (written 1601; published 1602) in Opera Omnia, Vol. 1, Heyder & Zimmer, 1858, p. 417 (title-page)

Men

“Either… the moving intelligences of the planets are weakest in those that are farthest from the sun, or… there is one moving intelligence in the sun, the common center, forcing them all round, but those most violently which are nearest, and that it languishes in some sort and grows weaker at the most distant, because of the remoteness and the attenuation of the virtue.”

Johannes Kepler book Mysterium Cosmographicum

Walter William Bryant, Kepler (1920), p. 17
Mysterium Cosmographicum (1596)

Intelligence , Distant , Sun

“If the moon and earth were not retained in their orbits by their animal force or some other equivalent, the earth would mount to the moon by a fifty-fourth part of their distance, and the moon fall towards the earth through the other fifty-three parts, and they would there meet, assuming, however, that the substance of both is of the same density.”

Johannes Kepler book Astronomia nova

As quoted by Bryant, ibid.
Astronomia nova (1609)

Animals , Parting

“But although the attractive virtue of the earth extends upwards, as has been said, so very far, yet if any stone should be at a distance great enough to become sensible compared with the earth’s diameter, it is true that on the motion of the earth such a stone would not follow altogether; its own force of resistance would be combined with the attractive force of the earth, and thus it would extricate itself in some degree from the motion of the earth.”

Johannes Kepler book Astronomia nova

As quoted by Bryant, ibid.
Astronomia nova (1609)